Specialists in the fitting of contact lenses often disagree as to the preferred procedure for analyzing and successfully modifying the peripheral curves, and their junction ridges which may exist on the back or ocular surface of such lenses.
In other words, contact lenses, as received by the specialist from the manufacturere, include not only the customery concave central curve, or base curve, which covers the pupilary surface of the eye, but also a peripheral portion comprising a secondary and sometimes a tertiary curve.
The peripheral curves are circular, curvilinear-in-section grooves formed in the back of the lens during manufacture. The junctions of the circular curves create ridges, which must ordinarily be eliminated by careful blending to fit the outer corneal surface of the eye in a comfortable fashion.
Radially outward from the peripheral portion, the lens margin recurves and rises slightly from the subjacent surface of the cornea to allow (1) tear fluid circulation beneath the lens and, (2) proper fitting of the lens on the cornea.
The corneal surface does not define a sphere. Instead, the corneal radius increases toward the edges resulting in a flattening of the surface. Thus, it is necessary to recurve the lens surface, to match the flattening of the cornea; otherwise, the lens would be too tight or would move on the corneal surface resulting in possible injury to the corneal surface.
Inasmuch as the peripheral poriton of the lens, as received from the manufacturer, frequently is not shaped to provide a comfortable fit, it is essential to be able to detect the presence, configuration and size of the peripheral curves in order to eliminate any surface malformations, which would lead to the wearer's discomfort, and to maximize tear circulation under the contact lens.
Heretofore, various expedients have been resorted to, such as inspecting the lens while it is held on a loupe and moving the lens-loupe combination back and forth against a light. While this technique will provide an experienced person with some indication of how well the curve junctions, or ridges, have been eliminated as a result of blending the peripheral portion of the lens, it gives no indication as to the radii of the peripheral curves, or grooves, bounded by the ridges. Accurate blending for maximum satisfaction is therefore impossible.
Still other procedures have utilized quite expensive optical systems of considerable sophistication and which are often time-consuming in use. Optical analyzers, furthermore, fail to provide an entire picture of the lens from edge to edge. This shortcoming is undesirable where, for example, a change is to be made in the percentage of central, or base curve, portion relative to the percentage of peripheral surface portion.
Of the following four patents turned up in a search, only the Koeniger patent is believed to be pertinent to the present device and process: Koeniger U.S. Pat. No. 3,794,429, 6/1974; McCormack, U.S. Pat. No. 3,820,899 6/1974; Padula et al., U.S. Pat. No. 3,917,391 11/1975; Volk, U.S. Pat. No. 4,149,801 4/1979.
Koeniger discloses a moderately complex system; and while its enclosed, magnification optics provide at least a partial profile capable of revealing malfomations, Koeniger's construction and operation are at substantial variance from the apparatus and method of the present invention.